Many cosmetics and personal care products, such as concealers, creams, lotions, and mascaras, are emulsions. Emulsions are a mixture of two or more immiscible liquids, such as water/oil or oil/silicone. These emulsions provide a means of dispersing a cosmetic agent, which may be lypophilic, within water or silicone which have a more appealing feel than oils. Although beneficial for administration, emulsions are typically difficult to formulate because of the demands on cosmetic products. In order to be commercially viable the emulsion must exhibit sufficient stability to survive shipping and storage environments. For example, cosmetics are often shipped under conditions where they are exposed to temperatures that are higher and lower than standard room temperature (72° F.). Products must be stable at these temperature extremes so that they can be delivered to the customer in a form that is suitable for commercial sale. In addition, commercially acceptable cosmetics must also be shelf stable, such that they do not exhibit an inordinate degree of separation when stored for long periods of time, typically one, two to three years, and even longer in some instances. The tendency of the immiscible liquids to separate out of the emulsion and coalesce frustrates these goals.
Stabilizers/emulsifiers and/or particles may be used to stabilize the emulsion. Stabilizers/emulsions tend to be amphiphilic, i.e., possessing both polar (hydrophilic) and non-polar (lypophilic) domains. The amphiphilic ingredient facilitates compatibility between two phases that may not otherwise be compatible to form a composition that is internally stable. Typically, the dispersed phase is stabilized within the continuous phase when the emulsifier/surfactant coats the interface between the dispersed and continuous phases to reduce the surface tension.
However, several problems exist with emulsifiers. Since the emulsion is stabilized by the interfacial adsorption of the surfactants (emulsifiers), the emulsion destabilizes if the emulsifiers de-adsorb from the interface or get lost in micelles before arriving at the interface. To address these complications, emulsifiers and/or particles are often added in excess to ensure they arrive at the interface. However this is less than an ideal solution given that the cost of compatibilizing agents is often high; they can be difficult to formulate; compositions containing them are sometimes prone to premature separation, and when used in high concentrations they can be somewhat irritating for consumers having sensitive skin.
WO2009139884A1 to Hein et al. outlines reacting natural butters (and other naturally occurring triglycerides) with glycerol, in the presence of a basic catalyst, during mixing to promote compatibility between lipid and water phases. The patent application does not claim any reactive polymeric materials.
WO 2010068891 to Bui et al. discloses a self-emulsifying mascara composition, in which the self-emulsification results in rheological properties which improve the lengthening properties of the cosmetic formula. The self-emulsification occurs within an aqueous formulation and involves functional polymers.
Accordingly, there is still a need for a method of stabilizing incompatible cosmetic compositions for extended periods without the drawbacks associated with conventional emulsifiers.
The foregoing discussion is presented solely to provide a better understanding of the nature of the problems confronting the art and should not be construed in any way as an admission as to prior art nor should the citation of any reference herein be construed as an admission that such reference constitutes “prior art” to the instant application.